OFDM/OFDMA系统的导频干扰方案

Pilot jamming scheme against OFDM/OFDMA

导频消除是干扰OFDM/OFDMA系统的有效方案,它以导频符号的180度相位偏移作为干扰信号,使目标信号的导频功率为0。但是,因为信道以及噪声等的影响,干扰信号的相位很难与目标信号的导频相位完全相反,导致干扰效果下降。首先将信道和发送延时的影响等效为干扰信号的相位偏差,然后分析了目标导频的抵消性能,给出了干扰后目标导频的幅度和相位分布,以及系统误符号率(SER)。理论分析和仿真结果表明:当干扰信号存在相位偏差时,该方案的抵消性能平均下降30%,SER性能平均下降10%。最后提出了一种基于分布式检测的导频干扰改进方案,利用检测反馈方式减小干扰信号相位偏差,从而提高干扰性能。

The pilot nulling is an effective jamming scheme against OFDM/OFDMA. It drived the pilot energy to zero by using a jamming signal that was the π-radian offset of the transmitted pilot tone value. But, because of the effect of the channel and the noise, the phase of the signal could hardly to set exactly, this would worsen the jamming effect. This paper analyzed the jamming effect when the jamming signal had phase deviation, deduced the distribution of the amplitude and the phase of the jammed signal, then there was the symbol error rate （SER） under the jamming. After simulation and analysis, there was a conclusion： when the jamming signal had phase deviation, the capability of the scheme to counteract the power decreased about 30% , the capability on SER decreased about 10%. Finally, this paper brought forward a novel scheme based on distribution detection. The schema reduced the phase deviation of interference signal using the detection feedback, thereby enhancing the performance of interference.